HIV-1 Rev activity on the MMTV RmRE in mouse mammary cells. A. Reporter activity in HC11 mouse mammary cells. Values are reported as described in Figure 2. B. Western blot of Rem and Rev expression in HC11 cells. Similar expression of the GFP-fusion proteins was observed as determined using antibodies specific for GFP (upper panel) or actin (lower panel). Size markers are given in kilodaltons.